THE latest apparent flap be tween the FBI and the NYPD turns on a factor that the intelligence world sometimes shares with the real-estate business: What matters is location, location, location.

For years, the New York Police Department and the Federal Bureau of Investigation have been bickering about NYPD access to secret and top-secret intelligence about potential terrorist threats to the city. The bureau will only let the department store such data if it's kept in an FBI-approved Sensitive Compartmented Information Facility, or SCIF.

The Washington Post reported Saturday that the FBI, after six years of stonewalling Police Commissioner Raymond Kelly's request, has finally agreed to let the NYPD install a SCIF vault in Manhattan for One Police Plaza.

What the report didn't say is that the NYPD has for several years had an FBI-approved vault for secret (though not top-secret) information - but in Brooklyn. The story also omitted the fact that the NYPD has had access to FBI-stored secret and top-secret information for at least that long.

But the article did quote Kelly complaining that "controlling information is power, and they [the FBI] don't want to let it go."

Deputy Police Commissioner Paul Browne told me yesterday that Kelly was referring to the legacy of disputes (now largely resolved) between the feds and the NYPD, calling the SCIF flap (or flappette) and other disputes "ancient history."

The brouhaha, in other words, is just another chapter in the history of lousy FBI/NYPD relations - which (though by no means perfect) have been steadily on the mend since November 2005, when FBI Director Robert Mueller traveled to New York to discuss the tensions directly with Kelly.

There is little doubt that the NYPD has had to push hard for the access to classified information it now has. For many years after 9/11, the FBI resisted NYPD demands for better and more timely intelligence, says Michael A. Sheehan, former NYPD deputy commissioner for counter-terrorism.

In "Crush the Cell," his new book about fighting terrorism, Sheehan writes that, when he joined the department in 2004, the NYPD had very little access to the kind of sensitive intelligence information it needed to protect New Yorkers from terrorist attack. So he decided to build a SCIF at the department's counterterrorism center in Brooklyn.

When the FBI balked at helping him build such a facility or certifying it, Sheehan (a former commander of a US Army Special Forces hostage-rescue unit who'd also held a top State Department counterterrorism job) sought help from old friends in Washington, recruiting assistance from Navy intelligence and the Department of Homeland Security.

That SCIF can now store intelligence that is classified secret, but not top secret. But it's in Brooklyn - with traffic, up to an hour's round-trip drive from Kelly's office.

Sheehan also directed a detective on the FBI-led Joint Terrorism Task Force to form a seven-person team to access classified information in the FBI's SCIF in Manhattan, not far from One Police Plaza, and to brief him each morning on incidents of information relating to potential terror threats to New York.

The FBI was willing to share sensitive information at its offices in downtown New York - as long as it kept control. Combined with the Brooklyn SCIF, "this was kind of a jerry-rigged, Rube Goldberg system, not perfect by any means," Sheehan told me yesterday. But by the time he left his post two years ago, he said, "we were getting the information we needed."

FBI approval of a SCIF at One Police Plaza means that top-secret information will soon be readily available to Kelly and other top NYPD officials. That's unlikely to end all the lingering tensions between the bureau and the NYPD, detectives and FBI agents agree. But it will be one less thing to fight over.

"And that means we'll all spend less time fighting one another and more time fighting the terrorists and other bad guys instead," says Sheehan.